linux-kernel - Re: [PATCH] KVM: selftests: Ignore KVM 5-level paging support for VM_MODE_PXXV48

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Message-ID: <ed65de29-a07a-f424-937e-38576e740de7@redhat.com>
Date:   Thu, 28 May 2020 13:55:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sergio Perez Gonzalez <sergio.perez.gonzalez@...el.com>,
        Adriana Cervantes Jimenez <adriana.cervantes.jimenez@...el.com>,
        Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH] KVM: selftests: Ignore KVM 5-level paging support for
 VM_MODE_PXXV48_4K

On 28/05/20 04:15, Sean Christopherson wrote:
> Explicitly set the VA width to 48 bits for the x86_64-only PXXV48_4K VM
> mode instead of asserting the guest VA width is 48 bits.  The fact that
> KVM supports 5-level paging is irrelevant unless the selftests opt-in to
> 5-level paging by setting CR4.LA57 for the guest.  The overzealous
> assert prevents running the selftests on a kernel with 5-level paging
> enabled.
> 
> Incorporate LA57 into the assert instead of removing the assert entirely
> as a sanity check of KVM's CPUID output.
> 
> Fixes: 567a9f1e9deb ("KVM: selftests: Introduce VM_MODE_PXXV48_4K")
> Reported-by: Sergio Perez Gonzalez <sergio.perez.gonzalez@...el.com>
> Cc: Adriana Cervantes Jimenez <adriana.cervantes.jimenez@...el.com>
> Cc: Peter Xu <peterx@...hat.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index c9cede5c7d0de..74776ee228f2d 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -195,11 +195,18 @@ struct kvm_vm *_vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
>  	case VM_MODE_PXXV48_4K:
>  #ifdef __x86_64__
>  		kvm_get_cpu_address_width(&vm->pa_bits, &vm->va_bits);
> -		TEST_ASSERT(vm->va_bits == 48, "Linear address width "
> -			    "(%d bits) not supported", vm->va_bits);
> +		/*
> +		 * Ignore KVM support for 5-level paging (vm->va_bits == 57),
> +		 * it doesn't take effect unless a CR4.LA57 is set, which it
> +		 * isn't for this VM_MODE.
> +		 */
> +		TEST_ASSERT(vm->va_bits == 48 || vm->va_bits == 57,
> +			    "Linear address width (%d bits) not supported",
> +			    vm->va_bits);
>  		pr_debug("Guest physical address width detected: %d\n",
>  			 vm->pa_bits);
>  		vm->pgtable_levels = 4;
> +		vm->va_bits = 48;
>  #else
>  		TEST_FAIL("VM_MODE_PXXV48_4K not supported on non-x86 platforms");
>  #endif
> 

Queued, thnaks.

Paolo